In my experience, that happens when the Home Editor Align function does not place the item exactly on the surface to which the item is attached, or on which it rests. So, when you place an item, always switch to the mode which has the Align function, and use it before de-selecting the item.Chairs and benches remain yellow in placement mode and can't be interacted with in the outdoor portion of the glade. They work fine inside the underground tower.